1. Field of the Invention
The present invention relates to a wafer supporting and/or conveying apparatus used in a wet cleaning apparatus for semiconductor devices.
2. Discussion of Related Art
A conventional wafer wet treatment apparatus for cleaning wafers is constructed in such a manner that a wafer is loaded in an inner bath located inside of an external tank, a cleaning solution flows into the bath from the bottom, flows over the bath, and then discharged from the external tank or recirculated in the tanks, to thereby clean the wafer. Here, the wafer is loaded in a wafer supporter carrying a plurality of wafers, and the wafer supporter is conveyed into the bath. A conventional bath used in the wafer cleaning apparatus such as the above-described one is disclosed in U.S. Pat. No.5,071,776, and wafer supporter is described in U.S. Pat. No.5,011,041, which has the U-shape sides.
In the conventional wafer wet cleaning apparatus, the cleaning solution flows into the bath through a flow control board which is the bottom of a cleaning treatment tank, cleans the wafer loaded in the wafer supporter, and then flows over the bath to a discharge recess. The cleaning solution discharged through the discharge recess is discarded or recirculated.
As semiconductor devices are highly integrated, the wafer cleaning technique and apparatus become more important. This is because even a slight amount of contamination due to the wafer cleaning apparatus affects the reliability of the device. This decreases wafer cleaning effect, and produces poor chips. Furthermore, as the diameter of wafer becomes wider, large-size bath is required. Thus, efforts to optimize the bath and other parts of the cleaning apparatus have been made in order to reduce the size of the cleaning apparatus.
For this, the shape of the supporter for supporting and conveying a wafer has been changed from the cassette shape shown as in FIG. 1 into the boat shape 21 shown in FIG. 2. By doing so, the area occupied by the wafer supporter in the bath, and the contact portion of the wafer and supporter are minimized, to thereby remove contamination sources of particles externally introduced from the bath.
The cassette shown in FIG. 1 is constructed in such a manner that sidewalls 11 and 12 are faced to each other in a specific distance, and a wafer 10 is supported by a plurality of protrusions 13, 14, 15 and 16 formed on the sidewalls in a specific interval. With the boat shown in FIG. 2, chucks 24 and 25 hold the side edges of the wafer, and convey it to the bath. Chucks 24 and 25 may also hold boat 21, or wafer only.
In the aforementioned conventional method, the cassette or boat for supporting the wafer, or chuck for holding it in the bath can be the external contamination source. For example, the wafer may be contaminated by coming into contact with the boat. With the bath of the above-described over flowing system, because the contamination source is located under the wafer, contamination materials are moved from the source to the overall surface of the wafer along the flowing line of the cleaning solution when it flows in the bath. These contaminations on the wafer, due to the supporter located under the wafer, or chuck holding the side and bottom of wafer, result in poor semiconductor device.